more tests

test.c

@@ -1,11 +1,24 @@
 //usr/bin/env cc -o test "$0" && ./test; exit
+
+// (run this file directly with `./test.c` in most shells; if that
+// doesn't work, run it with `sh test.c`)
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
 
+int file_contents_equal(char* path, char* contents) {
+    char command[200];
+    snprintf(command, sizeof(command),
+             "[ \"%s\" == \"$(cat %s)\" ]", contents, path);
+    return system(command) == 0;
+}
+
 // integration tests
 int main() {
     assert(system("echo about:blank > fs/mnt/tabs/create") == 0);
+    assert(file_contents_equal("fs/mnt/tabs/last-focused/url", "about:blank"));
+    assert(system("file fs/mnt/tabs/last-focused/screenshot.png") == 0);
     
     assert(1); printf("Done!\n"); 
 }